Aluminum beryllium alloy



Patented Sept. 2, 1930 UNITED sTA'rEs mm 8. 43cm n WILLIAM- L. mic, or CLEV LAN 01110, assmnon's 'ro Amman: company or memos, orrn'rsnunen; PENNSYLVANIA, A com-'0- RATION O1 PENNSYLVANIA ALUMINUM nEiaYLLIUu ALLOY Ro Drawing. Original application flied November 21!, 1926, Serial No. 150,141. Divided and this appli cation filed December 19, 1928. Serial No. 327,176.

This application is a division of our copendin application, Serial No. 150,141, filed- Novem er 22, 1926, which has resulted in' the grant of Patent No. 1,716, 943, dated June 11, 1929, in which there is claimed the method herein disclosed of treating aluminumrberyl- 'lium alloys.

-- for which light aluminum base a1 oys are used, but because of its present high cost, beryllium cannot be used in large quantities as an alloying constituent in competition with less expensive alloying constituents. W e have discovered, however, that by alloying relatively small quantities of beryllium with aluminum there result inexpensive light aluminum base alloys, which, when heat-treated (ill in a particular manner discovered by us, possess materially higher physical properties than previously known similar aluminumberyllium alloys. As to this heat treatment, we have discovered that aluminum beryllium alloys, particularly when made from quite pure metals, possess a marked increase in hardness and tensile strength when heated tor a substantial period of time at a temperature slightly below the aluminum-berylium eutectic temperature and then quenched in Water or another suitable quenching medium. We have alsodiscovered that alumi- Ilium-beryllium alloys, when thus hea treated, age harden, both naturally at room tern eratures, and artificially at temperatures not i her than about 200 G.

In t e practice of the leature-ot curinvention having to do with a. method oil heat treating aluminum base alloys containing beryllium, such an alloy is heated to a tern-r perature slightly below: the melting'point of the most fusib e constituent of.- the-"alloy,

which may be that ofthe'aluminum-beryllium eutectic, and is maintained at such temperature for a substantialperiod off time, the alloy being then quenched at, or substantially at, the temperature to which it was heated.

We have found that the temperature to which.

the alloy is heated and at which it is maintained may vary from about 550 C. to slightly below 645 C., which latter is about the PATENT ()Frc g aluminum-beryllium eutectic temperature.

The period of time during which the alloy is maintained at an elevated temperature varies withits size and with the heating temperature and the beryllium content of the alby The time of heat-treatment will also vary according asthe alloy is in the cast condition or has been mechanically deformed. However, this may be readily determined by practice and from the illustrative exam les of the invention presently to be describe After an aluminum-beryllium alloy has been so heated and quenched, it is age hardened either naturallv at room temperature or artificially at an elevated temperature not higherthan about 200 C. We have found that an aluminum-beryllium alloy, for example a binary alloyin the form of a casting, age hardens naturally at room tempera ture quite rapidly, and that this hardening is often substantially complete after one or two days." However, it is sometimes advanta'geous to effect the age hardening artificiallyat elevated temperatures.

As has been stated, the effect of this heattreatmentis to substantially" increase the hardness and tensile strength of the alloy.

ils cast, the alloy may contain undissolved beryllium, which, upon being heated in the manner explained, tends to dissolve and form .asolid solution; up to the solubility limit at the temperature to which it is heated. When the alloy is quenched from this temperature the solid solution is retained at room temperature, and, upon aging, the excess con stituent which was dissolved at the hi her temperature tends to precipitate in the orm of very small particles which harden and stifi'en the matrix, thereby increasing the, strength and hardness of the alloy.

Aluminum-beryllium alloys such as here- YOU 1280 C., in molten aluminum at about 1100 C. until the beryllium is dissolved. The use of small amounts of a flux such as barium chloride facilitates introduction of the beryllium. By using higher temperatures, rich aluminum-beryllium alloys containing 10, 25 or 50 per cent or more of berylliummay be prepared in this way for use in the subsequent preparation of aluminuni-beryllium alloys having lower beryllium content, or for use themselves without subsequent alloying.

The invention will now be further explained with reference to specific examples with the understanding, however, that the examples are given by way of illustrations and not as limitations of the invention.

In the following table there are given in the first column the beryllium content of a number of aluminum-beryllium alloys, specimens of which were prepared by casting the alloys in iron molds to give chill cast slabs about one-fourth of an inch/thick. The Brinell hardness values of these alloys as cast were determined by using a 10 millimeter ball under a load of 500 kilograms, and are given in the second column of the table. The several specimens were then all heated for 24 hours at a temperature of 631 C. and then quenched in water, after which their Brinell hardness values given in the third column of the table were determined in the manner just explained. Thereafter the specimens were all permitted to age naturally for two days at room temperature, and their Brinell hardness values given in the last column of the table were then determined.

This table shows that the Brinell hardness values of the specimen containing J013"o beryllium do not vary materially with heattreatment, the hardness value of the specimen when quenched and aged being substantially the same as when cast. However, the specimen having a beryllium content of 025% when quenched and aged had a Brinell hardness materially higher than as cast or as quenched, and this is likewise true of the several specimens having beryllium contents greater than 025%. From this it appears that aluminum base alloys containing not less than about 025% beryllium are capable of having their hardness and strength substantially increased by heat-treating them according to this invention.

Several tests were made to determine the arrests effect of heating the alloys at temperatures above and below that used in heating the specimens given in the above table. A specimen of an alloy containing 075% beryllium after being heated for 18 hours at 657 0., quenched in water and aged three days at room temperature was found to have a Brinell hardness of 24 immediately after quenching, and of 15 after aging. Other specimens of the same alloy after being heated for 18 hours at 600 C. and quenched in water were found to have an average Brinell hardness value of 25 as quenched, and of 40.2 after aging at room temperature, showing a decrease in Brinell hardness as compared to the sample which was heated at 031 C. but nevertheless showing a substantial increase in hardness as compared to that as quenched.

Still further samples of the same aluminum-beryllium alloy after being heated for 18 hours at 600 (1. and quenched in water were found to have a Brinell hardness of 25.4. One sample was artificially aged for three hours at 150 C. and found to then have a Brinell hardness of 34.4. Another sample showed a Brinell hardness of only 27.1 after aging 50 hours at room temperature, showing that the age hardening is more rapid at elevated than at room temperatures.

Similar tests have been made of various other alloys containing different percentages of beryllium with results of the same general order as typified by the examples just eX- plained. As showing that the invention is applicable to aluminum-beryllium alloys containing much larger percentages of beryllium, an alloy containing 23% beryllium after being heated for 18 hours at 638 C. and quenched in water was found to have a Brinell hardness of 30, and after being aged for two days at room temperature the Brinell hardness was found to be 38.

The invention is applicable not only to chill castings made of aluininuiii-beryllium alloys, but also to sand castings, as shown by the following example. Samples of sand cast aluminum-beryllium alloys containing .572; beryllium showed in the cast condition an average tensile strength of about 12,000 pounds per square inch and a Brinell hardness of 21. After aging 11 days at room temperature the samples showed no appreciable change in strength or hardness. Other samples of the same alloy after being heated for 30 hours at 632 C. and quenched in water had a tensile strength of 13,000 pounds per square inch and a Brinell hardness of 23. These heat-treated samples were then permitted to age naturally at room temperature for 11 days, when it was found that their average tensile strength was 17,000 pounds per square inch and their Brinell hardness 86.

The samples thus far given have been of cast aluminum-beryllium alloys, but the invention contemplates wrought, rolled. or

dlt

otherwise worked alloys. As illustrative of.

this,'an allo containing 0.075% beryllium was forged ot to a bar about five-elghths of an inch square, and after annealin was it was 34.

This same'heat treatment process can be applied with advantage to sheet rolled from the aluminum-beryllium alloys. Such alloys were made up to contain varying amounts of beryllium, ranging from 0.0125 to 23.0 per cent, using aluminum of about 99.95% purlty. We found that sheet 0.064 inches thick can be rolled readily from small ingots of these.

alloys. Two samples illustrative of the beneficial effect of our heat treatment upon sheet material 0.064 inches thick are given in the following table:

Annealed state Heattmated state Berylllum percent Yield Tensile Elonga- Yield Tensile Elonga point strength tlon point strength tion In this table the sheet in its annealed state had been annealed at 300 (1., and in its heat-treated state it had been heated for one and one-half hours at 625 C., quenched in.

cold water, and aged several weeks at room temperature. The yield points and tensile strengths are given in pounds per square inch, and the elongations in per cents in two inches.

Heat treatment of aluminum-beryllium alloy sheet also serves to increase the corrosion resistance as determined by theusual salt spray method. in applyin this test the E1011 tlon e-' fore cor- -roslon Elon tlon a ter corrosion Condition Annealed- Heat treated 625 0., and quenched. ts rolled. Heat treated 625 0., and quenched.

These figures show that heat-treated sheet specimens are much less adected by the salt spray than sheets which are in the as rolled or annealedcondition.

As previously indicated, a further feature of our invention has to do with the provision of ternary or more'complex aluminum alloys containing beryllium. We have found very useful and beneficial effects are produced by the addition of beryllium to aluminum base alloys containing silicon, copper, magnesium,

magnesium and silicon, magnesium and copper, and magnesium, copper andsilicon. Depending upon the particular alloy in question, the effect of the addition of beryllium to these alloys may, for example, be to confer age hardening characteristics where they did not exist before, to increase the age hardening characteristics already inherent in the alloy, and to increase the total hardness of the alloy.

As shown by the following example, beryllium confers age-hardening properties upon chill cast aluminum-copper alloys. Such an alloy containing 4% copper andno beryllium after being chill cast showed no appreciable increase in hardness after standing several'days at room temperature. However, when .05% of beryllium was added to an aluminumbase alloy containing 4% copper and the alloy chill cast,'the Brinell hardness increased from 4.6 immediately after casting to 69 after'the sample was aged naturally for five days at room temperature. Similarly, the Brinell hardness of an aluminum alloy containing\3% copper and 0.05% beryllium increased from 48 as cast to 64 after aging eight days at room temperature. After heating samples of, the last mentioned aluminum-copper-beryllium alloy for eight hours at 589 C. and uenching in water, it was found that the, rinell 'hardness as quenched was 58, and after aging two days at'room temperature it was found that the hardness had risen to 87. Results of the same order were obtained by varying the beryllium as well as the copper content of other aluminum base alloys containing these constituents.

Heat-treated pure aluminum-copper alloys show distinct hardening at room temperature. F or example, an aluminum-copper alloy containing 4% copper was heat-treated at 550 (land quenched. The hardness of the as quenched specimen was 63. After aging twenty-five days at room temperature, the hardness had increased to 79. The addition of beryllium to such an alloy causes an increase in this effect. Theaddition of 0.05% beryllium to the foregoing alloy caused the hardness to increase from 65 immediately after quenching from 550 C. to

99 after aging twenty-five days at room temperature.

It is shown in the followingexample that the addition of beryllium to aluminum-copper alloys has the further advantage of reducing theliability of the alloy burning during its forging or heat-treatment. The heating curve showing the increase in temperature per unit of time of an aluminumcopper alloy containing 6% copper normally shows an arrest when the alloy reaches a temperature of about 548 C., this being due to the fusion of the aluminum-CuAl eutectic at this temperature. When .81% of beryllium was added to an aluminum-copper alloy containing 6% copper and the resulting alloy heated, it was found that the first arrest in the heating curve was at 56a C. and that forgings of this alloy heat-treated for two and one-half hours at 554 C. showed no signs of burning. This indicates that the copper and beryllium had probably combined in some way, because otherwise any l'rce (JuAl present in the alloy would have melted at or below the aluminum-CuAh eutectic temperature of about 548 C.

\Ve have found that in some cases heat treating periods much shorter than some of those used in the preceding examples produce equally beneficial results. As illustra tive of this, samples of a forged aluminumcopper-beryllium alloy containing 6% copper and .8l% beryllium were heat-treated for two and one-half hours at 554 C. and quenched in water. As determined by using a 1000 kilogram load, the Brinell hardness of this alloy as quenched was 69, and after aging naturally at room temperature for twenty-four hours it had risen to 98. At the end of forty-eight hours the Brinell hardness was 99, and at the end of twelve days it was 101. The average tensile strength of forged samples of this alloy after aging twelve days was found to be about 52,000 pounds per square inch, and the elongation to be 25% in two inches.

As to the efieets of beryllium on aluminum base alloys containing additional alloying constituents other than copper, we have found by a number of tests that theaddition of silicon to aluminum-heryllium alloys results in an increase of their final hardness after quenching. An aluminum base alloy containing'l o beryllium, .577fma rnesium and 1% silicon was found to have a Brinell hardness of 42 as cast and of 54 after aging for one week at room temperatures. the latter being materially higher than that of a similar alloy not containing beryllium. After being heated for eighteen hours at 550 (1., quenched in water and aged for one week at room temperature the Brinell hardness of the aluminum-beryllium-magnesiinn-silicon alloy just described was found to be 74. An alloy of the same composition plus 4% copper showed as cast a Brinell hardness of 70. and after aging at room temperature for one week it showed a Brinell hardness of 84. Samples of this alloy, after being heated for fifty hours at 500 C. and quenched in water, showed as quenched a Brinell hardness of 57, and after aging at room tem rature for one week a Brinell hardness of 9 From the foregoing it clearly appears that certain aluminum base alloys containing beryllium, whether they are binary, ternary or more complex alloys, have their physical properties substantially increased by heating them for a substantial period at a temperature slightly below the melting point of the aluminum-beryllium eutectic, or in the case of the ternary and more complex alloys to a temperature slightly below the melting point of the most fusible constituent of the alloys, and then quenching them. In general, regardless of the temperature at which an aluminum-beryllium alloy may be treated, it is necessary to heat the alloy only long enough to cause substantial solution of the undissolved beryllium constituent. It is also evident from the foregoing examples of aluminum base ternary and more complex alloys containing beryllium that they possess substantial advantages whether or not they are heat-treated according to the method here provided. when it is desired to age the heattreated alloys at elevated temperatures, it is possible to quench them from the heat treating temperature in boiling water or other suitable medium at the desired temperature and to maintain them at this temperature for an appropriate length of time.

Throughout this specification, and 'in the appended claims, the expression aluminum base alloy is used to describe an alloy in which aluminum is the predominant constituent regardless of whether the alloy is binary, ternary, or of a more complex order.

No claim is made herein for aluminumberyllium alloys containing silicon and magnesium either separate or combined with each other or with other constituents. such claims being made in other applications in compllance with a requirement for division.'

According to the provisions of the patent statutes, we haveexplained the principle and mode of operation of our invention and have described numerous specific examples or" the manner in which it may be practiced. However we desire to have it understood that. within the scope of the appended claims, the invention may be practiced in alloys having compositions differing from those particularly described. 1

from about .025 to 1.00% beryllium, and also containing from about 3 to 6% copper.

In testimony whereof, we hereunto sign our names. I

ROBERT S. ARCHER. WILLIAM L. FINK. 

